Because updating Safari involves updating system files as well as the application itself, it will be a .pkg (package) file, requiring Installer to run if/when you decide you want to install it—rather than a .dmg (disk image) file that can be mounted and from which the application can simply be dragged to the Applications folder—but in any case, here's the working address for the Apple download source, courtesy of MacUpdate:
Safari6.1.3Lion.pkg 
